Telli is a fast-growing startup that builds AI voice agents for sales-driven B2C companies. The company relies on text-to-speech (TTS) capabilities with natural, multilingual voices and very low latency.

Their focus on B2C sales applications prioritizes voice quality, as the believability of their virtual agents can make or break a sale. As telli scaled, they needed a TTS solution that could scale with them, delivering exceptional quality and integrating effortlessly with their existing call infrastructure.

After searching through available options for TTS providers, they landed on Cartesia. Using Cartesia’s high-quality voice library and easy Pipecat integration, telli was able to get set up in just one hour—with dramatic results. Voice quality—and customer satisfaction—improved significantly, and advanced features like hyper-realistic voice cloning allowed them to expand their offerings. Their move to Cartesia has given telli a key advantage in a competitive market.

Customer background

• Company Name: telli

• Industry: AI-powered customer communications / SaaS

• Location: Germany, serving a global customer base

Launched in late 2024, telli empowers sales-driven B2C businesses to automate thousands of daily calls. Their AI voice agents handle tasks like booking appointments, qualifying warm leads, and re-engaging customers.

With a lean team, telli serves a diverse range of industries, including HVAC, solar, real estate, healthcare, and finance. Telli specializes in helping customers overcome common pain points like lead reachability, call capacity constraints, and high operational costs.

Challenges

As their client base grew, telli recognized the need for a TTS provider that could keep apace without compromising on the quality of the service. In their search, they kept their focus on a few critical criteria:

• Natural, human-like voices. A key part of improving customer engagement was ensuring voice agents sounded as real as live salespeople.

• Wide range of voices. With their clients serving diverse populations, telli’s clients rely heavily on a variety of personas, accents, and languages specific to their use cases.

• Ease of integration. Telli needed a solution that would integrate seamlessly with their Pipecat-based call manager without significant engineering effort.

• EU-based hosting. With telli operating out of Germany, data residency requirements made reliable, geo-specific hosting a must.

The solution

Telli’s team, already aware of Cartesia's reputation for superior voice quality, made a swift decision to adopt the platform. The integration was remarkably fast and addressed their challenges directly.

• Seamless integration: Native support for integrations like Pipecat allowed telli's engineering team to implement Cartesia as their TTS provider with minimal effort—taking only about one hour to get up and running.

• Superior voice quality & diversity: Telli immediately gained access to Cartesia's extensive library of natural-sounding voices, including high-quality German voices, which were a significant improvement. This allowed them to offer clients a "big toolbox" of personas to choose from for A/B testing and use-case-specific agents (e.g., inbound vs. outbound agents).

• Advanced voice cloning: Telli became an early adopter of Cartesia's voice cloning feature. This enabled them to offer a powerful new service: cloning the voice of a client's top-performing sales representative. This hyper-personalization bridges the gap between AI and human agents, building customer trust through a consistent experience.

• EU hosting & reliability: For telli’s privacy-conscious German and European clients, Cartesia's EU hosting capabilities were a critical feature, satisfying data residency requirements without sacrificing performance or reliability.

Deployment

The transition to Cartesia was exceptionally smooth and efficient, reflecting the platform's developer-first design.

• The process: The implementation was a straightforward technical task. Leveraging Cartesia's native Pipecat integration, the engineering team easily integrated it into their existing pipeline.

• Timeline: The entire process was completed in approximately one hour. This speed was crucial for a fast-scaling company like telli, as it required minimal reassignment of engineering resources.

• Collaboration: Telli noted that Cartesia's top-notch support was a major benefit. Quick responses to feature requests and bug reports created a strong sense of partnership and reliability.

Results

The qualitative and business impacts of switching to Cartesia have been profound and immediate:

• Massive improvement in customer satisfaction: This was the primary and most significant result. Clients immediately noticed the enhanced, natural-sounding voices. Telli receives constant granular feedback through shared Slack channels, with customers praising the new voices. 

• Establishment of a key competitive advantage: In a crowded AI voice market, Cartesia’s quality has become a cornerstone of telli's value proposition. Feedback from customers on Cartesia’s voices has been overwhelmingly positive, making voice quality a key driver in winning and keeping business.

• Creation of new, high-value service offerings: The voice cloning feature, powered by Cartesia, has allowed telli to provide a unique, personalized service that deepens client relationships and delivers a more authentic customer experience.

• Increased end-customer engagement & conversion: Telli’s Ennie Raguse states that the voice is what gets the call to convert. The natural, low-latency conversations engage end-customers effectively, preventing the "uncanny valley" effect that causes people to disengage from robotic-sounding AI.

In their words

"The voice is at the heart of what we do, so it has to be just right. With Cartesia and their voice cloning capabilities, we’ve been able to reach a new level of quality. Throughout, they've been a great partner to start with and to scale with. It's an easy-to-use text-to-speech tool that we'd definitely recommend for achieving brand-aligned, highly engaging conversations."

Ennie Raguse, Founders Associate, telli

A world-class partnership

The partnership between telli and Cartesia highlights how foundational technology can unlock significant product improvements and create a powerful competitive advantage. By switching to Cartesia, telli not only solved its immediate technical challenges but also elevated its entire product offering.